Cooling characteristics and thermal properties of kraft recovery boiler smelt

grantor: University of TorontoAn accurate prediction of smelt thermal state is crucial in the cooling of kraft recovery boiler smelt in order to prevent smelt-water explosion and shorten the cooling time. The smelt cooling process was systematically investigated in this study. A laboratory-scale experimental apparatus was constructed and used to conduct field experiments in a kraft mill with a running decanting floor recovery boiler. The molten smelt samples were collected from a smelt spout, and cooled in the experimental apparatus. By measuring the internal temperature histories, the cooldown characteristics were obtained and analyzed. The results showed that smelt cooling involves a slow heat transfer process and is mainly controlled by the rate of heat conduction within the smelt interior due to the low thermal conductivity of smelt. A transient 3-dimensional heat transfer model was also developed to analyze and predict the smelt cooling process. The results showed reasonably good agreement with the experimental data. Both experimental and simulation results indicated that the thermal conductivity of frozen smelt is well around 0.6 W/m°C.M.A.Sc